# Foil prank

Robert Kaplinsky kindly contributed this post.  We think it would make a great April Fools day activity. Check out his site for more great lesson ideas.

Watch this movie with your class:   foil_prank

### The Challenge(s)

• How much does it cost to cover this classroom in aluminum foil?

These questions may be useful in helping students down the problem solving path:

• What is a guess that is too low?
• What is a guess that is too high?
• What is your best guess?
• What shape are the objects in your section?
• How do you determine how much aluminum foil you will need to cover that shape?

### Consider This

There are many ways this problem could be implemented.  I suggest dividing the classroom into sections (perhaps with painter’s tape) and assigning several students to each section with the goal of determining how much aluminum foil would be needed to cover their section.  One assumption that should be made is that no aluminum foil overlap will be necessary.

The Common Core State Standards specifically reference that students should be able to find the surface area of rectangular and triangular prisms.  As such, you may need to place various objects around the room to provide a diverse set of objects to measure.  Your classroom is most likely full of rectangular prisms but may be missing triangular prisms.  Examples of triangular prisms include:

• empty and closed three-ring binders
• Toblerone chocolate boxes
• Folded and taped paper (when all else fails)

Cylinders are not specifically mentioned in the Common Core State Standards but that would be another useful object to find the surface area of.

Once each of the groups has determined what objects they have in their section, the next step will be to find each object’s surface area.  That will take some time as well as rulers and/or tape measures.  You can reduce the amount of time this takes by:

• Limiting the portion of the classroom students measure and having each section be smaller
• Setting restrictions as to what each group should measure (for example, not every cord or paper clip)
• Limiting each section to covering a specific number of items.

When all groups have finished calculating the surface area of the objects in their area, they should come up with a total surface area for their section.  It would be beneficial for each group to present one or two of their favorite objects and how they calculated the foil needed to cover it.  Once all of the groups have presented, have the class add all of the answers together to make a grand total for the class.

Using this information and the cost of the heavy duty aluminum foil, calculate the total cost.  Note that it is \$27.56 for two rolls of 150 square feet each.  That gives a unit rate of approximately 9.3 cents per square foot.

Enjoy and huge thanks to Robert Kaplinsky for this interesting and tricky activity.

CCSS: 6.G.4, 6.RP.2, 6.RP.3, 7.G.6, HSG.MG.1

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